Reference work entry
Precursor-miRNAs (pre-miRNA) refer to the hairpin precursors of miRNAs formed by the cleavage of primary miRNAs by DCGR8 and Drosha.
The 17–24 nt, single-stranded miRNAs are derived from longer, primary transcripts termed “pri-miRNAs.” The pri-miRNAs, which can be more than 1,000 nt in length, contain an RNA hairpin in which one of the two strands includes the mature miRNA. The hairpin, which typically comprises 60–120 nt, is cleaved from the pri-miRNA in the nucleus by the double-strand-specific ribonuclease, Drosha. The resulting pre-miRNA hairpins are transported to the cytoplasm via a process that involves Exportin-5. In cytoplasm, the pre-miRNA is further cleaved by the RNase III enzyme Dicer to generate a short, partially double-stranded RNA (miRNA:miRNA* duplex). The mature miRNA is taken up by a protein complex that is similar, if not identical, to the RNA-Induced Silencing Complex (RISC) that supports RNA interference (RNAi), and...
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